<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8"/>
        <title></title>
    </head>
    <body>
        <script type="text/javascript">
            var arr = [1,2,3];
            var arr0=arr.map(function(item,index){
                return item-1;
            });
            console.log(arr0);
</script>
    </body>
</html>